The setting and immobilization of bone fractures with simple splints and slings has been practiced since ancient times. Modem biomedical engineering has yielded increasingly advanced orthopedic fixation technology, including various internal and external devices, such as pins, braces, plates, and screws. Many of these devices are temporary, and require removal after surgery or at any of various times throughout the healing process. Some devices such as internal screws are often left in place indefinitely, due to the cost, potential complications, and difficulty of removing them.
Typically, orthopedic hardware is removed at some time following surgery for various reasons. For example, a fastener embedded in bone can act as a stress riser, which may increase the risk of an undesired fracture in the bone proximate the fastener location. Additionally, over time, the position of a fastener can shift away from the initial embedded position, which may result in an infection or other negative side effect. At the very least, an un-removed fastener may simply cause discomfort, such as by conducting cold temperatures, or creating pain and irritation in the tissue surrounding the fastener. Although less likely, tan un-removed fastener may result in the potential inconvenience associated with metal detector false alarms.
In addition to potentially negative consequences caused by leaving hardware fixed in a patient's bone, some negative effects may be caused during the installation of the hardware. For example, a fastener may become damaged during the process of insertion, such as stripping the head or breaking the head off entirely. Such damage to the head can make further insertion and/or extraction of the fastener highly problematic.
The nature of bone itself also presents some challenges. As the bone heals, it tends to encase the fastener more tightly, which can increase the torque required to loosen the fastener from the bone. The bone may also encroach upon the head of the fastener making it difficult to access. Another problem arises from the hollow nature of bones. When removing a screw, once the threaded portion has been unscrewed from the distal cortex of the bone, there may be insufficient resistance offered by the screw head to keep the driver engaged. Moreover, even if the screw can be extracted to the point where the proximal end of the threaded portion comes into contact with the proximal cortex of the bone, the bone may have grown tightly around the shank, which can impede further progress. Accordingly, there may be insufficient resistance to keep the driver engaged in the head for the threads to bite.
Other challenges analogous to those discussed above may also exist in non-medical positional fixation applications, such as applications involving materials such as wood, metal, and plastic, or any applications where a reliable and minimally invasive apparatus, system, or method for insertion and/or removal of a fastener is desired.